Method for producing non-oriented silicon steel for driving motor

Abstract

The application discloses a production method of non-oriented silicon steel for driving motor. In the non-oriented silicon steel, Si is 2.5-3.5%, Al is 0.8-1.5%, Mn is 0.5-1.0%, P is 0.02-0.04%, C is smaller than 0.002%, S is smaller than 0.0015%, and N is smaller than 0.002%; the non-oriented silicon steel is obtained through heat treatment, shot blasting and pickling, cold rolling, annealing and coating of a hot-rolled steel coil; the heat treatment comprises: aging treatment, heat preservation at 700-800 DEG C for 20-40 h; normalizing, heat preservation at 900-980 DEG C for 3-5 min; during annealing, the cold-rolled strip steel is sent into an electromagnetic induction heating device, transverse magnetic heating is adopted, the target heating temperature is 900-950 DEG C, and the heating rate is controlled to be 100-150 DEG C / s; then heat preservation is carried out at the target heating temperature for 1-4 h under the protection of nitrogen or argon; and then cooling is carried out to room temperature.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of steel material preparation, and relates to a production method of non-oriented silicon steel for driving motors. BACKGROUND

[0002] Non-oriented silicon steel is the core material of the rotor of an electric motor and a generator working in a rotating magnetic field, and is required to have good magnetic properties, including low iron loss and high magnetic induction, and the improvement of the magnetic properties is also a core research topic of the non-oriented silicon steel for a long time.

[0003] With the rapid development of new energy vehicles, the operation efficiency and output torque of the driving motors thereof are continuously improved, and therefore the non-oriented silicon steel for the motor cores is required to have extremely low iron loss and high magnetic induction.

[0004] At present, in order to reduce the iron loss of the non-oriented silicon steel product, the content of alloy elements such as Si and Al is usually increased to improve the resistivity of the material, so as to reduce the iron loss of the product. However, with the increase of the content of alloy elements such as Si and Al, the magnetic permeability of the material is reduced, and the magnetic induction is also reduced, which cannot meet the requirements of the driving motor of the new energy vehicle on the non-oriented silicon steel. SUMMARY

[0005] The application aims to provide a production method of non-oriented silicon steel for driving motors.

[0006] To achieve the above-mentioned application purpose, an embodiment of the application provides a production method of non-oriented silicon steel, and the chemical composition of the non-oriented silicon steel includes, in terms of mass percentage, Si 2.5% to 3.5%, Al 0.8% to 1.5%, Mn 0.5% to 1.0%, P 0.02% to 0.04%, C<0.002%, S<0.0015%, and N<0.002%.

[0007] The non-oriented silicon steel is obtained by subjecting a hot-rolled steel coil to a heat treatment process, a shot blasting and pickling process, a cold rolling process, an annealing process and a coating process.

[0008] The heat treatment process includes an aging treatment step and a normalizing step, in the aging treatment step, the hot-rolled steel coil is kept at 700 to 800℃ for 20 to 40h, and in the normalizing step, the hot-rolled steel coil is kept at 900 to 980℃ for 3 to 5min.

[0009] In the annealing process, the cold-rolled strip steel obtained in the cold-rolling process is sent into an electromagnetic induction heating device, transverse magnetic heating is adopted, the target heating temperature of the cold-rolled strip steel is 900-950℃, and the heating rate is controlled to be 100-150℃ / s; then the cold-rolled strip steel is kept at the target heating temperature for 1-4h under the protection of nitrogen or argon; and then the cold-rolled strip steel is cooled to room temperature.

[0010] As a further improvement of the embodiment of the present application, in the heat treatment process, the aging treatment step is prior to the normalizing step; or, the normalizing step is prior to the aging treatment step.

[0011] As a further improvement of the embodiment of the present application, in the annealing process, after the cold-rolled strip steel is heated by the electromagnetic induction heating device, the cold-rolled strip steel is sent into a furnace roll heat preservation system, wound into a roll and kept warm.

[0012] As a further improvement of the embodiment of the present application, in the annealing process, the cooling rate when the cold-rolled strip steel is cooled to room temperature is controlled to be 1-5℃ / min.

[0013] As a further improvement of the embodiment of the present application, in the annealing process, after the keeping warm is finished, the cooling water pipes around the cold-rolled strip steel are opened to cool the cold-rolled strip steel, the temperature of the cold-rolled strip steel is monitored in real time, and the temperature and flow of the cooling water in the cooling water pipes are controlled according to the monitored temperature of the cold-rolled strip steel.

[0014] As a further improvement of the embodiment of the present application, in the annealing process, when the transverse magnetic heating is performed, the temperature of the cold-rolled strip steel is monitored in real time, and the frequency and current of the electromagnetic induction heating device are controlled according to the monitored temperature of the cold-rolled strip steel.

[0015] As a further improvement of the embodiment of the present application, in the annealing process, the electromagnetic induction heating device comprises an induction coil, a high-frequency power supply, a temperature sensor and a controller, the high-frequency power supply and the temperature sensor are connected with the controller, the high-frequency power supply is connected with the induction coil and provides alternating current, the induction coil surrounds the cold-rolled strip steel, and the magnetic force line direction is perpendicular to the rolling direction of the cold-rolled strip steel, the temperature sensor is used to monitor the temperature of the cold-rolled strip steel in real time, and the controller is used to control the frequency and current of the high-frequency power supply according to the monitored temperature of the cold-rolled strip steel.

[0016] As a further improvement of the embodiment of the present application, in the cold-rolling process, the strip steel obtained after the shot blasting and pickling process is heated to 80-120℃, and then cold-rolled into a cold-rolled strip steel by a twenty-roll mill.

[0017] As a further improvement of the embodiment of the present application, the thickness of the non-oriented silicon steel is 0.20-0.35mm, the average grain size is 100-160µm, the yield strength is 420-470MPa, and the tensile strength is 500-560MPa.

[0018] As a further improvement of the embodiment of the present application, the magnetic induction B 50 ≥1.68T, the iron loss P 1.5 / 50 ≤2.0W / kg; P 1.0 / 400 ≤12.0W / kg; P 1.0 / 800 ≤20.0W / kg.

[0019] Compared with the prior art, the beneficial effects of the present application are:

[0020] (1) In the chemical composition design scheme of the present application, by controlling the higher Si and Al contents, the purpose of improving the resistivity and reducing the iron loss can be achieved; by adding a certain amount of Mn and P, the purpose of improving the yield strength of the non-oriented silicon steel can be achieved to meet the service safety requirements of the high-speed driving motor of new energy; by controlling the C, S and N contents, the influence of the second phase precipitates in the non-oriented silicon steel on the structure and texture during the recrystallization process can be reduced as much as possible, and the magnetic properties of the finished product can be improved;

[0021] (2) In the production method of the present application, first, by long-term aging treatment of the hot-rolled steel coil, AlN and MnS second phase precipitates are precipitated and coarsened to form coarse AlN-MnS composite precipitates, which effectively promote the full growth of grains during the recrystallization process after cold rolling and annealing, and create favorable conditions for the nucleation and growth of the λ texture (<100> / / ND); by normalizing treatment and controlling the normalizing temperature and time, the ferrite grains in the hot-rolled steel coil are coarsened, providing a basis for the full growth of grains during the recrystallization process after cold rolling and annealing; by the electromagnetic induction heating device, the nucleation points of the grains can be increased, especially the nucleation points of the λ texture (<100> / / ND), combined with transverse magnetic heating, since the magnetic field direction is perpendicular to the rolling direction, the transverse magnetic heating can provide additional driving force for the grain boundary migration through the magnetic crystal anisotropy, so that the λ texture (<100> / / ND) grains grow more easily under the action of the magnetic field; further combined with high-temperature long-time holding for 1-4h, not only the grain size of the finished product after annealing can be improved, but also the growth of the λ texture (<100> / / ND) grains can be effectively promoted, thereby avoiding the λ texture (<100> / / ND) being swallowed by the γ texture (<111> / / ND), increasing the proportion of the λ texture (<100> / / ND) in the non-oriented silicon steel finished product, and significantly reducing the proportion of the adverse γ texture (<111> / / ND), thereby reducing the iron loss and improving the magnetic induction strength. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 A metallographic structure photo of the non-oriented silicon steel of embodiment 1 of the present application;

[0023] Figure 2 A metallographic structure photo of the non-oriented silicon steel of embodiment 2 of the present application;

[0024] Figure 3 A metallographic structure photo of the non-oriented silicon steel of embodiment 3 of the present application. DETAILED DESCRIPTION

[0025] The technical solutions of the present application will be further described in combination with specific embodiments.

[0026] An embodiment of the present application provides a non-oriented silicon steel. The chemical composition of the non-oriented silicon steel comprises, in percentage by mass: Si 2.5%-3.5%, Al 0.8%-1.5%, Mn 0.5%-1.0%, P 0.02%-0.04%, C <0.002%, S <0.0015%, and N <0.002%.

[0027] The functions and effects of each element in the chemical composition are described as follows.

[0028] Si: Si is a solid solution strengthening element. An increase in the content of Si can increase the strength of the non-oriented silicon steel, and can also increase the resistivity of the non-oriented silicon steel and reduce the iron loss. In the present application, the content of Si is controlled to be 2.5%-3.5%.

[0029] Al: An increase in the content of Al can increase the resistivity of the non-oriented silicon steel and reduce the iron loss, but can reduce the magnetic induction intensity. In the present application, the content of Al is controlled to be 0.8%-1.5%. In addition, Al is easy to form coarse AlN precipitates with N, thereby reducing the iron loss of the steel plate.

[0030] Mn: Mn can increase the resistivity of the non-oriented silicon steel, thereby reducing the finished product iron loss. An increase in the content of Mn can increase the strength of the non-oriented silicon steel, thereby meeting the use requirements of high-speed rotation of new energy driven motors. In the present application, the content of Mn is controlled to be 0.5%-1.0%.

[0031] P: P can effectively increase the yield strength of the non-oriented silicon steel, thereby meeting the safety requirements of the rotor core of new energy driven motors under high-speed rotation conditions. However, with an increase in the contents of Si and Al, an excessively high content of P can increase the brittleness of the material and reduce the cold rolling workability. Therefore, in the present application, the content of P is controlled to be 0.02%-0.04%.

[0032] C: The increase of C content will lead to the formation of carbide second phase precipitates in the annealing process of non-oriented silicon steel, which will inhibit the grain recrystallization growth in the annealing process, and will also lead to magnetic aging in the use process of non-oriented silicon steel, which will worsen the magnetic properties of the finished product, and then lead to the increase of core heating and the reduction of motor efficiency. Therefore, the C content is controlled to be C < 0.002% in the present application.

[0033] The increase of S and N content will lead to the decline of the magnetic properties of non-oriented silicon steel, including the increase of iron loss and the reduction of magnetic induction intensity. In the present application, the content of S and N is controlled to be S < 0.0015% and N < 0.002%.

[0034] In the above chemical composition design scheme, by controlling the high Si and Al content, the purpose of improving the resistivity and reducing the iron loss of the material can be achieved; by adding a certain amount of Mn and P, the purpose of improving the yield strength of non-oriented silicon steel can be achieved to meet the service safety requirements of high speed of new energy driven motor; by controlling the content of C, S and N, the influence of the second phase precipitates in non-oriented silicon steel on the structure and texture in the recrystallization process can be reduced as much as possible, and then the magnetic properties of the finished product can be improved.

[0035] In non-oriented silicon steel, the texture of the finished product of non-oriented silicon steel after annealing includes γ texture (<111> / / ND) and λ texture (<100> / / ND).

[0036] Among them, the λ texture (<100> / / ND) is easier to magnetize, and the higher the texture strength is, the higher the magnetic induction intensity is. However, the deformation energy storage of the λ texture (<100> / / ND) is low, and it has no advantage in the recrystallization process.

[0037] And the γ texture (<111> / / ND) is difficult to magnetize, and the higher the texture strength is, the lower the magnetic induction intensity is. And the deformation energy storage of the γ texture (<111> / / ND) is high, and it has the advantage in the recrystallization process.

[0038] At present, continuous annealing is usually used in the production of non-oriented silicon steel, and the holding time of continuous annealing is limited. Compared with the λ texture (<100> / / ND), the γ texture (<111> / / ND) has high deformation energy storage and is easy to nucleate and grow in continuous annealing, while the λ texture (<100> / / ND) has low deformation energy storage and insufficient recrystallization driving force, which is easily swallowed by the γ texture (<111> / / ND) in the annealing and recrystallization process, and then the proportion of the λ texture (<100> / / ND) is reduced, and the magnetic properties of the finished product of non-oriented silicon steel are deteriorated.

[0039] In view of this, an embodiment of the present application further provides a production method for the above non-oriented silicon steel.

[0040] In the production method, the non-oriented silicon steel is obtained from the hot-rolled steel coil through a heat treatment process, a shot blasting and pickling process, a cold rolling process, an annealing process and a coating process.

[0041] The heat treatment process comprises an aging treatment step and a normalizing step.

[0042] In the aging treatment step, the hot-rolled steel coil is kept at 700-800 ℃ for 20-40 h. Through long-time aging treatment and control of the aging temperature, the AlN and MnS second phases are allowed to precipitate and coarsen, forming relatively coarse AlN-MnS precipitates with a size of 2-5 μm, so as to avoid the formation of nanosized, fine and dispersed second phase precipitates in the subsequent cold rolling and annealing process. The coarsening of the second phase precipitates can effectively promote the grain growth in the annealing recrystallization process, and create favorable conditions for the nucleation and growth of the low-energy λ texture (<100> / / ND), thereby improving the magnetic properties of the finished non-oriented silicon steel product.

[0043] In the normalizing step, the hot-rolled steel coil is kept at 900-980 ℃ for 3-5 min. Through normalizing and control of the normalizing temperature and time, the recrystallization of the hot-rolled deformed ferrite is promoted, and the non-uniformity of the hot-rolled structure and texture is improved. After normalizing, the coarse ferrite grains provide a basic condition for the grain growth in the cold rolling and annealing recrystallization process.

[0044] In the annealing process, the cold-rolled strip steel obtained in the cold rolling process is sent into an electromagnetic induction heating device, and transverse magnetic heating is adopted. The target heating temperature of the cold-rolled strip steel is 900-950 ℃, and the heating rate is controlled at 100-150 ℃ / s. Then, the cold-rolled strip steel is kept at the target heating temperature for 1-4 h in a nitrogen or argon protective atmosphere, and then cooled to room temperature.

[0045] The electromagnetic induction heating has the characteristics of high efficiency and energy saving. Through electromagnetic induction heating, the energy consumption can be significantly reduced, the heating time can be shortened, and the production efficiency can be improved. Although the electromagnetic induction heating can improve the strength of the λ texture (<100> / / ND) to a certain extent, due to the rapid heating of the electromagnetic induction heating, the cold-rolled deformed structure of various texture types can obtain sufficient recrystallization driving force in unit time, which makes the grain size decrease after annealing, and thus leads to high iron loss of the finished non-oriented silicon steel product after annealing.

[0046] The application firstly makes AlN and MnS second phase precipitates precipitate and coarsen through long time aging treatment of the hot-rolled steel coil, forms coarse AlN-MnS composite precipitates, effectively promotes the full growth of grains in the recrystallization process after cold rolling and annealing, and creates favorable conditions for the nucleation and growth of the lambda texture (<100> / / ND); through normalizing treatment and controlling the normalizing temperature and time, the ferrite grains in the hot-rolled steel coil are coarsened, which provides a basis for the full growth of grains in the recrystallization process after cold rolling and annealing; through rapid heating by the electromagnetic induction heating device, the nucleation points of grains, especially the nucleation points of the lambda texture (<100> / / ND) are increased, combined with transverse magnetic heating, since the magnetic field direction is perpendicular to the rolling direction, the transverse magnetic heating can provide additional driving force for the grain boundary migration through the magnetic crystal anisotropy, so that the lambda texture (<100> / / ND) grains grow more easily under the action of the magnetic field; further combined with high temperature long time holding for 1-4h, not only the grain size of the finished product after annealing can be increased, but also the growth of the lambda texture (<100> / / ND) grains can be effectively promoted, so that the lambda texture (<100> / / ND) is not swallowed by the gamma texture (<111> / / ND), the proportion of the lambda texture (<100> / / ND) in the non-oriented silicon steel finished product is increased, the proportion of the adverse gamma texture (<111> / / ND) is significantly reduced, so that the iron loss is reduced and the magnetic induction intensity is increased.

[0047] Specifically, in the heat treatment process, the sequence of aging treatment and normalizing can be interchanged, that is, the aging treatment step can be performed before the normalizing step; or the normalizing step can be performed before the aging treatment step.

[0048] Both the aging treatment and the normalizing treatment can coarsen and precipitate the AlN and MnS second phase, avoid the formation of nanoscale MnS second phase precipitates, promote the nucleation and growth of the <100> / / ND texture beneficial to the magnetic property, and improve the magnetic induction intensity of the non-oriented silicon steel finished product. In actual production, the sequence can be adjusted according to the equipment conditions and the like.

[0049] Preferably, in the annealing process, after heating by the electromagnetic induction heating device, the cold-rolled steel strip is sent into the furnace coil heat preservation system, wound into a coil and heat preserved. Through the furnace coil heat preservation system, long time uniform heat preservation of the steel coil can be realized, the temperature of the steel coil is ensured to be uniform during the heat preservation process, so that the lambda texture (<100> / / ND) is fully grown, the lambda texture (<100> / / ND) is not swallowed by the gamma texture (<111> / / ND), the strength of the lambda texture (<100> / / ND) in the non-oriented silicon steel finished product is increased, so that the magnetic induction intensity of the finished product is improved while the iron loss is reduced.

[0050] Specifically, the furnace coil insulation system comprises an insulation furnace, a winding device and an atmosphere control device. The winding device is arranged in the insulation furnace and is used to wind the cold-rolled strip into a coil to facilitate uniform insulation for a long time. The atmosphere control device is used to provide a protective atmosphere such as nitrogen or argon to the insulation furnace to prevent the cold-rolled strip from being oxidized.

[0051] Preferably, in the annealing process, the cooling rate to room temperature is controlled to be 1-5℃ / min. By controlling the cold-rolled strip to cool slowly at a low rate, residual thermal stress is avoided in the grain interior.

[0052] Preferably, in the annealing process, cooling is performed using a cooling system.

[0053] The cooling system comprises a cooling water pipe and a temperature control device. The cooling water pipe is located at the outer periphery of the insulation furnace. Since the cold-rolled strip is still located in the insulation furnace during cooling, the cooling water pipe is also located around the cold-rolled strip. The temperature control device is used to monitor the temperature of the cold-rolled strip in real time and control the temperature and flow of the cooling water in the cooling water pipe according to the monitored temperature of the cold-rolled strip.

[0054] Specifically, in the annealing process, after the insulation is completed, the cooling water pipe around the cold-rolled strip is turned on to cool the cold-rolled strip, and the temperature of the cold-rolled strip is monitored in real time, and the temperature and flow of the cooling water in the cooling water pipe are controlled according to the monitored temperature of the cold-rolled strip.

[0055] Preferably, in the annealing process, during transverse magnetic heating, the temperature of the cold-rolled strip is monitored in real time, and the frequency and current of the electromagnetic induction heating device are controlled according to the monitored temperature of the cold-rolled strip, so as to accurately control the temperature and heating rate of the cold-rolled strip.

[0056] Specifically, the electromagnetic induction heating device comprises an induction coil, a high-frequency power supply, a temperature sensor and a controller. The high-frequency power supply and the temperature sensor are connected to the controller, the high-frequency power supply is connected to the induction coil and provides an alternating current for the induction coil, the induction coil surrounds the cold-rolled strip, and the magnetic field direction is perpendicular to the rolling direction of the cold-rolled strip, the magnetic field is distributed transversely, a high-frequency induced current is generated transversely to the rolling direction of the cold-rolled strip, and a high-frequency eddy current is formed, thereby generating heat to rapidly heat the cold-rolled strip. The temperature sensor is used to monitor the temperature of the cold-rolled strip in real time. The controller is used to control the frequency and current of the high-frequency power supply according to the monitored temperature of the cold-rolled strip.

[0057] In the shot blasting and pickling process, after the strip steel cooled to room temperature after the heat treatment process, most of the oxide scale, rust and dirt on the surface of the strip steel are removed by shot blasting, and a certain roughness is formed on the surface of the strip steel. Further, through pickling, the residual oxide scale and rust layer on the surface of the strip steel are dissolved.

[0058] Preferably, in the cold rolling process, the strip steel after the shot blasting and pickling process is heated to 80-120°C, and then cold-rolled into a cold-rolled strip steel with a thickness of 0.20-0.35 mm by a twenty-roller mill.

[0059] It is detected that the finished non-oriented silicon steel prepared by the above production method has a thickness of 0.20-0.35 mm, an average grain size of 100-160 µm, a yield strength of 420-470 MPa, a tensile strength of 500-560 MPa, a magnetic induction B 50 ≥ 1.68 T, a core loss P 1.5 / 50 ≤ 2.0 W / kg; P 1.0 / 400 ≤ 12.0 W / kg; P 1.0 / 800 ≤ 20.0 W / kg.

[0060] Therefore, under the combined action of the aforementioned chemical composition and production process, the grain size is controlled to be 100-160 µm, which can ensure that the non-oriented silicon steel has low core loss and high magnetic induction strength, and the comprehensive optimization of the magnetic properties and strength of the non-oriented silicon steel is realized under the conditions of reducing the cost and production difficulty, so that the non-oriented silicon steel can meet the application requirements on the drive motor of the new energy vehicle.

[0061] The detailed description listed above is only a specific description of the feasible embodiments of the present application, and is not used to limit the protection scope of the present application. Equivalent embodiments or changes made without departing from the spirit of the present application should be included in the protection scope of the present application.

[0062] Three embodiments of the present application are provided below to further illustrate the technical solutions of the present application. Of course, these embodiments are only a part of the numerous changed embodiments contained in the present application, but not all.

[0063] Embodiment 1

[0064] The embodiment provides a non-oriented silicon steel, which has a chemical composition including, in terms of mass percentage, Si 3.0%, Al 1.0%, Mn 0.6%, P 0.03%, C 0.0018%, S 0.0010%, and N 0.0012%.

[0065] The non-oriented silicon steel is obtained from a hot-rolled steel coil with a thickness of 2.0 mm by sequentially passing through a heat treatment process, a shot blasting and pickling process, a cold rolling process, an annealing process, and a coating process. The processes are specifically described as follows.

[0066] (1) Heat treatment process

[0067] Firstly, aging treatment is performed, and the hot-rolled steel coil is kept at 780°C for 35 h. Then, normalizing is performed, and the hot-rolled steel coil is kept at 950°C for 4 min.

[0068] (2) Shot blasting pickling process

[0069] After the strip steel after the heat treatment process is cooled to room temperature, the strip steel surface is removed by shot blasting, pickling, and rust layer.

[0070] (3) Cold rolling process

[0071] The strip steel after the shot blasting pickling process is heated to 100°C, and then is cold-rolled into a cold-rolled strip steel with a thickness of 0.20mm by a twenty-roll mill.

[0072] (4) Annealing process

[0073] First, the cold-rolled strip steel obtained by the cold rolling process is sent into the electromagnetic induction heating device, and transverse magnetic heating is adopted, the target heating temperature of the cold-rolled strip steel is 900°C, the heating rate is controlled to be 120°C / s, and the temperature of the cold-rolled strip steel is monitored in real time during the transverse magnetic heating, and the frequency and current of the electromagnetic induction heating device are controlled according to the monitored temperature of the cold-rolled strip steel.

[0074] The electromagnetic induction heating device includes an induction coil, a high-frequency power supply, a temperature sensor, and a controller. The high-frequency power supply and the temperature sensor are connected to the controller, the high-frequency power supply is connected to the induction coil and provides alternating current for the induction coil, the induction coil surrounds the cold-rolled strip steel, and the magnetic force line direction is perpendicular to the rolling direction of the cold-rolled strip steel, the magnetic field is distributed transversely, high-frequency induction current is generated in the transverse direction perpendicular to the rolling direction of the cold-rolled strip steel, and high-frequency eddy current is formed, thereby generating heat. The temperature sensor is used to monitor the temperature of the cold-rolled strip steel in real time. The controller is used to control the frequency and current of the high-frequency power supply according to the monitored temperature of the cold-rolled strip steel.

[0075] Then, the cold-rolled strip steel is sent into the furnace coil insulation system, wound into a steel coil, and kept at the target heating temperature for 2h in a protective atmosphere of nitrogen or argon.

[0076] The furnace coil insulation system includes an insulation furnace, a winding device, and an atmosphere control device. The winding device is arranged in the insulation furnace, and the winding device is used to wind the cold-rolled strip steel into a coil. The atmosphere control device is used to provide a protective atmosphere such as nitrogen or argon into the insulation furnace.

[0077] Then, the steel coil is sent into the cooling system and slowly cooled to room temperature at a rate of 3°C / min.

[0078] The cooling system includes a cooling water pipe and a temperature control device. The cooling water pipe is located outside the insulation furnace. The temperature control device is used to monitor the temperature of the cold-rolled strip steel in real time, and the temperature and flow of the cooling water in the cooling water pipe are controlled according to the monitored temperature of the cold-rolled strip steel.

[0079] Specifically, after the heat preservation ends, cooling water pipes around the cold-rolled strip are opened to cool the cold-rolled strip, and the temperature of the cold-rolled strip is monitored in real time, and the temperature and flow of the cooling water in the cooling water pipes are controlled according to the monitored temperature of the cold-rolled strip.

[0080] (5) Coating process

[0081] After the strip steel after the annealing process is cooled, an insulating coating is applied to the upper and lower surfaces of the strip steel, and an oriented silicon steel finished product is obtained.

[0082] The magnetic and mechanical properties of the oriented silicon steel finished product obtained in this embodiment are detected, including:

[0083] A, by metallographic structure observation, the metallographic structure photograph is as shown in Figure 1 The average grain size measured is 100-120µm;

[0084] B, the iron loss and magnetic induction intensity are detected by GB / T 3655 standard, the magnetic induction B 50 ≥1.68T, the iron loss P 1.5 / 50 ≤1.8W / kg; P 1.0 / 400 ≤10.0W / kg; P 1.0 / 800 ≤18.0W / kg.

[0085] C, the yield strength and tensile strength are detected by GB / T 228.1 standard, the yield strength is 420-470MPa, and the tensile strength is 500-560MPa.

[0086] Example 2

[0087] The embodiment provides an oriented silicon steel, which comprises, in mass percentage: Si 2.8%, Al 1.2%, Mn 0.8%, P 0.025%, C 0.0017%, S 0.0009%, and N 0.0013%.

[0088] The oriented silicon steel is obtained from a hot-rolled steel coil with a thickness of 2.0mm by sequentially passing through a heat treatment process, a shot blasting and pickling process, a cold rolling process, an annealing process and a coating process. The following will specifically describe each process.

[0089] (1) Heat treatment process

[0090] First, the aging treatment is performed, and the hot-rolled steel coil is kept at 750℃ for 38h. Then, the normalizing is performed, and the hot-rolled steel coil is kept at 950℃ for 4min.

[0091] (2) Shot blasting and pickling process

[0092] After the strip steel which has undergone the heat treatment process is cooled to room temperature, the strip steel is sequentially subjected to shot blasting and pickling to remove the oxide scale and rust layer on the surface of the strip steel.

[0093] (3) Cold rolling process

[0094] The strip steel which has undergone the shot blasting and pickling process is heated to 100°C, and then is cold-rolled into a cold-rolled strip steel with a thickness of 0.25 mm by a twenty-roller rolling mill.

[0095] (4) Annealing process

[0096] Firstly, the cold-rolled strip steel obtained in the cold rolling process is sent into an electromagnetic induction heating device, transverse magnetic heating is adopted, the target heating temperature of the cold-rolled strip steel is 925°C, the heating rate is controlled to be 125°C / s, during the transverse magnetic heating, the temperature of the cold-rolled strip steel is monitored in real time, and the frequency and current of the electromagnetic induction heating device are controlled according to the monitored temperature of the cold-rolled strip steel.

[0097] The electromagnetic induction heating device includes an induction coil, a high-frequency power supply, a temperature sensor and a controller. The high-frequency power supply and the temperature sensor are connected with the controller, the high-frequency power supply is connected with the induction coil and provides an alternating current for the induction coil, the induction coil surrounds the cold-rolled strip steel, the magnetic force line direction is perpendicular to the rolling direction of the cold-rolled strip steel, the magnetic field is distributed in a transverse direction, a high-frequency induction current is generated in the transverse direction perpendicular to the rolling direction of the cold-rolled strip steel, and a high-frequency eddy current is formed, so that heat is generated. The temperature sensor is used to monitor the temperature of the cold-rolled strip steel in real time. The controller is used to control the frequency and current of the high-frequency power supply according to the monitored temperature of the cold-rolled strip steel.

[0098] Then, the cold-rolled strip steel is sent into a furnace coil heat preservation system, is wound into a steel coil, and is preserved at the target heating temperature for 2h in a protective atmosphere of nitrogen or argon.

[0099] The furnace coil heat preservation system includes a heat preservation furnace, a winding device and an atmosphere control device. The winding device is arranged in the heat preservation furnace and is used to wind the cold-rolled strip steel into a coil. The atmosphere control device is used to provide a protective atmosphere such as nitrogen or argon into the heat preservation furnace.

[0100] Then, the steel coil is sent into a cooling system and is slowly cooled to room temperature at a rate of 2°C / min.

[0101] The cooling system includes a cooling water pipe and a temperature regulation device. The cooling water pipe is located outside the heat preservation furnace. The temperature regulation device is used to monitor the temperature of the cold-rolled strip steel in real time and to control the temperature and flow of the cooling water in the cooling water pipe according to the monitored temperature of the cold-rolled strip steel.

[0102] Specifically, after the heat preservation ends, cooling water pipes around the cold-rolled strip are opened to cool the cold-rolled strip, and the temperature of the cold-rolled strip is monitored in real time, and the temperature and flow of the cooling water in the cooling water pipes are controlled according to the monitored temperature of the cold-rolled strip.

[0103] (5) Coating process

[0104] After the strip steel after the annealing process is cooled, an insulating coating is applied to the upper and lower surfaces of the strip steel to obtain the finished non-oriented silicon steel.

[0105] The magnetic and mechanical properties of the finished non-oriented silicon steel obtained in this embodiment are detected, including:

[0106] A. By observing the metallographic structure, the metallographic structure photograph is as shown in Figure 2 , and the average grain size measured is 120-150 µm;

[0107] B. The iron loss and magnetic induction intensity are detected by GB / T 3655 standard, and the magnetic induction B 50 ≥1.69T, the iron loss P 1.5 / 50 ≤1.8W / kg; P 1.0 / 400 ≤11.0W / kg; P 1.0 / 800 ≤19.0W / kg.

[0108] C. The yield strength and tensile strength are detected by GB / T 228.1 standard, and the yield strength is 420-470 MPa, and the tensile strength is 500-560 MPa.

[0109] Example 3

[0110] This embodiment provides a non-oriented silicon steel, which includes, in terms of mass percentage, Si 3.2%, Al 0.9%, Mn 0.7%, P 0.035%, C 0.0015%, S 0.0005%, and N 0.0012%.

[0111] The non-oriented silicon steel is obtained from a hot-rolled steel coil with a thickness of 2.0 mm by sequentially passing through a heat treatment process, a shot blasting and pickling process, a cold rolling process, an annealing process, and a coating process. The following will specifically describe each process.

[0112] (1) Heat treatment process

[0113] First, the aging treatment is performed, and the hot-rolled steel coil is kept at 720°C for 30h. Then, the normalizing is performed, and the hot-rolled steel coil is kept at 950°C for 4min.

[0114] (2) Shot blasting and pickling process

[0115] After the strip steel cooled to room temperature after the heat treatment process, in turn through the shot blasting, pickling, remove the strip steel surface scale and rust layer.

[0116] (3) cold rolling process

[0117] The strip steel after the shot blasting pickling process is heated to 100℃, and then is cold rolled into a cold rolled strip steel with a thickness of 0.30mm by a twenty-roll mill.

[0118] (4) annealing process

[0119] First, the cold rolled strip steel obtained in the cold rolling process is sent into the electromagnetic induction heating device, transverse magnetic heating is adopted, the target heating temperature of the cold rolled strip steel is 950℃, the heating rate is controlled to be 110℃ / s, the temperature of the cold rolled strip steel is monitored in real time during the transverse magnetic heating, and the frequency and current of the electromagnetic induction heating device are controlled according to the monitored temperature of the cold rolled strip steel.

[0120] The electromagnetic induction heating device includes an induction coil, a high-frequency power supply, a temperature sensor and a controller. The high-frequency power supply and the temperature sensor are connected with the controller, the high-frequency power supply is connected with the induction coil and provides alternating current for the induction coil, the induction coil surrounds the cold rolled strip steel, the magnetic force line direction is perpendicular to the rolling direction of the cold rolled strip steel, the magnetic field is distributed transversely, high-frequency induced current is generated in the transverse direction perpendicular to the rolling direction of the cold rolled strip steel, and high-frequency eddy current is formed, thereby generating heat. The temperature sensor is used to monitor the temperature of the cold rolled strip steel in real time. The controller is used to control the frequency and current of the high-frequency power supply according to the monitored temperature of the cold rolled strip steel.

[0121] Then, the cold rolled strip steel is sent into the furnace coil heat preservation system, is wound into a steel coil, and is heat preserved at the target heating temperature for 3h in a protective atmosphere of nitrogen or argon.

[0122] The furnace coil heat preservation system includes a heat preservation furnace, a winding device and an atmosphere control device. The winding device is arranged in the heat preservation furnace, and is used to wind the cold rolled strip steel into a coil. The atmosphere control device is used to provide a protective atmosphere such as nitrogen or argon into the heat preservation furnace.

[0123] Then, the steel coil is sent into the cooling system and is slowly cooled to room temperature at a rate of 4℃ / min.

[0124] The cooling system includes a cooling water pipe and a temperature regulation device. The cooling water pipe is located outside the heat preservation furnace. The temperature regulation device is used to monitor the temperature of the cold rolled strip steel in real time, and to control the temperature and flow of the cooling water in the cooling water pipe according to the monitored temperature of the cold rolled strip steel.

[0125] Specifically, after the heat preservation ends, the cooling water pipes around the cold-rolled strip are opened to cool the cold-rolled strip, and the temperature of the cold-rolled strip is monitored in real time, and the temperature and flow of the cooling water in the cooling water pipes are controlled according to the monitored temperature of the cold-rolled strip.

[0126] (5) Coating process

[0127] After cooling the strip after the annealing process, insulating coatings are applied to the upper and lower surfaces of the strip to obtain the finished non-oriented silicon steel product.

[0128] The magnetic and mechanical properties of the finished non-oriented silicon steel product obtained in this embodiment are detected, including:

[0129] A. By metallographic structure observation, the metallographic structure photograph is as shown in Figure 1 The average grain size measured is 130-160 µm;

[0130] B. The iron loss and magnetic induction intensity are detected by GB / T 3655 standard, and the magnetic induction B 50 ≥ 1.69 T, the iron loss P 1.5 / 50 ≤ 2.0 W / kg; P 1.0 / 400 ≤ 12.0 W / kg; P 1.0 / 800 ≤ 20.0 W / kg.

[0131] C. The yield strength and tensile strength are detected by GB / T 228.1 standard, and the yield strength is 420-470 MPa, and the tensile strength is 500-560 MPa.

[0132] As can be seen from the above embodiments 1-3, the non-oriented silicon steel prepared by the production method of the present application not only has low iron loss and high magnetic induction intensity, excellent magnetic properties, but also low alloy cost, small production difficulty, and low production cost, meeting the application requirements on the driving motor of new energy vehicles.

[0133] It should be understood that although the present specification is described in terms of embodiments, each embodiment does not contain only one independent technical solution, and the description of the specification is only for clarity, and those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can be appropriately combined to form other embodiments that can be understood by those skilled in the art.

[0134] The detailed description listed above is only a specific description of the feasible embodiments of the present application, and is not intended to limit the protection scope of the present application, and any equivalent embodiments or changes made without departing from the spirit of the present application should be included in the protection scope of the present application.

Claims

1. A method of producing a non-oriented silicon steel, characterized by, The chemical composition of the non-oriented silicon steel includes, in mass percentage, Si 2.5%-3.5%, Al 0.8%-1.5%, Mn 0.5%-1.0%, P 0.02%-0.04%, C <0.002%, S <0.0015%, and N <0.002%. The non-oriented silicon steel is obtained by subjecting a hot-rolled steel coil to a heat treatment process, a shot blasting and pickling process, a cold rolling process, an annealing process, and a coating process. The heat treatment process includes an aging treatment step and a normalizing step, in the aging treatment step, the hot-rolled steel coil is kept at 700-800℃ for 20-40h, and in the normalizing step, the hot-rolled steel coil is kept at 900-980℃ for 3-5min. In the annealing process, the cold-rolled strip steel obtained in the cold rolling process is sent into an electromagnetic induction heating device, transverse magnetic heating is adopted, the target heating temperature of the cold-rolled strip steel is 900-950℃, and the heating rate is controlled to be 100-150℃ / s; then the cold-rolled strip steel is kept at the target heating temperature for 1-4h under the protection of nitrogen or argon atmosphere; and then the cold-rolled strip steel is cooled to room temperature.

2. The production method of non-oriented silicon steel according to claim 1, characterized by, In the heat treatment process, the aging treatment step is prior to the normalizing step. Alternatively, the normalizing step is prior to the aging treatment step.

3. The production method of non-oriented silicon steel according to claim 1, characterized by, In the annealing process, after being heated by the electromagnetic induction heating device, the cold-rolled strip steel is sent into a furnace coil heat preservation system, wound into a coil, and kept for heat preservation.

4. The production method of non-oriented silicon steel according to claim 1, characterized by, In the annealing process, the cooling rate when cooled to room temperature is controlled to be 1-5℃ / min.

5. The method of producing a non-oriented silicon steel according to claim 4, characterized by, In the annealing process, after the heat preservation is completed, the cooling water pipes around the cold-rolled strip steel are opened to cool the cold-rolled strip steel, the temperature of the cold-rolled strip steel is monitored in real time, and the temperature and flow of the cooling water in the cooling water pipes are controlled according to the monitored temperature of the cold-rolled strip steel.

6. The production method of non-oriented silicon steel according to claim 1, characterized by, In the annealing process, when transverse magnetic heating is performed, the temperature of the cold-rolled strip steel is monitored in real time, and the frequency and current of the electromagnetic induction heating device are controlled according to the monitored temperature of the cold-rolled strip steel.

7. The method of producing a non-oriented silicon steel according to claim 6, characterized by, In the annealing process, the electromagnetic induction heating device includes an induction coil, a high-frequency power supply, a temperature sensor, and a controller, the high-frequency power supply and the temperature sensor are connected to the controller, the high-frequency power supply is connected to the induction coil and provides alternating current, the induction coil surrounds the cold-rolled strip steel, and the magnetic force line direction is perpendicular to the rolling direction of the cold-rolled strip steel, the temperature sensor is used to monitor the temperature of the cold-rolled strip steel in real time, and the controller is used to control the frequency and current of the high-frequency power supply according to the monitored temperature of the cold-rolled strip steel.

8. The method of producing a non-oriented silicon steel according to claim 1, characterized in that, In the cold rolling process, the strip steel subjected to the shot blasting and pickling process is heated to 80-120℃, and then cold-rolled into a cold-rolled strip steel by a twenty-roll rolling mill.

9. The method of producing a non-oriented silicon steel according to claim 1, characterized in that, The non-oriented silicon steel has a thickness of 0.20-0.35mm, an average grain size of 100-160µm, a yield strength of 420-470MPa, and a tensile strength of 500-560MPa.

10. The method of producing a non-oriented silicon steel according to claim 1, characterized in that, The magnetic induction B of the non-oriented silicon steel 50 ≥ 1.68 T, iron loss P 1.5 / 50 ≤ 2.0 W / kg; P 1.0 / 400 ≤ 12.0 W / kg; P 1.0 / 800 ≤ 20.0 W / kg.

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